The present invention relates to an approach for discovering the torque produced by an internal combustion engine, and to a means for utilizing the indication thus produced.
Even before the internal combustion engine became prevalent, users of prime moves have sought means for discovering the power output of the prime mover. Such an indication is extremely useful in properly adjusting the engine, and for operating it in a practical, economical manner. In theory, it has long been known that the power output of an engine having a movable element such as a piston could be calculated in accordance with the acronym "PLAN" wherein P represents the pressure per unit area upon the piston; L the length of the crankshaft stroke; A the area of the piston and N the speed in revolutions per minute. By ignoring the last term, the torque of the engine could be calculated.
In practice, however, making use of this simple formula has often been difficult. In the main this has been due to the practical difficulties of monitoring the internal operations of the engine. Nonetheless apparatus were developed for steam engines which monitored the differential pressure existing on either side of a piston. In effect, it was recognized that as the piston moved it compressed gaseous material either above or below it. Where the material, such as steam, drove the piston work was being done, and accordingly torque generated. However, insofar as the piston was exhausting steam from a cylinder, work was being done within the engine and accordingly a negative torque produced. Engineers recognized that by substracting one pressure from another the net work being done upon the piston could be arrived at. In this manner various sorts of instruments were devised for indicating engine work, and it became commonplace for steam engines to include mechanical devices incorporating a card and a pen for tracing a chart which could then be interpreted as indicating engine work.
With the development of the internal combustion engine, however, the problems of ascertaining engine work or power increased. In particular, the extremely high temperatures and pressures encountered in combustion chambers made it difficult to mechanically couple the chamber interiors to measuring instruments. Further in contradistinction to the steam engine, 4-cycle internal combustion engines do not provide a manifestation which can be readily interpreted as engine power. In particular, cylinder pressures during intake, compression and exhaust strokes all reflect work being done by the piston; in other words, negative engine output. Only the pressure arising during the power stroke reflected power output. Accordingly, the average pressure developed within the cylinder was practically meaningless, and it was extremely difficult to provide instrumentation which sensed only pressure arising during the power stroke.
For the foregoing reasons it has for decades been conventional to measure engine output by developing some manifestation of the actual torque outputted by the engine. This was conventionally done by means of a brake such a a Prony brake which comprised means for frictionally engaging a wheel driven by an engine. By tightening the engagement to the point of stalling the engine, the maximum torque of the engine could be read by means of a scale or the like. Then, by other means, the speed of the engine could be developed and the speed and torque figures used in order to calculate actual engine power.
In recent years the advance of technology has made it possible to couple transducers to the combustion chamber of an internal combustion engine and process the signals produced thereby. For instance, an electrical signal may be produced which reflects the instantaneous pressure within a cylinder, and other electronic means associated with the engine for determining at what point in the overall engine cycle the pressure arises. Then, by properly processing the signals together it is possible to attribute various pressures to different cycles, and accordingly to calculate the pressure arising due to work done by, and work done on, the engine. Finally, this information is processed to arrive at a figure reflecting engine torque and/or power.
It will be appreciated that it would be extremely useful to provide an indication of torque or power to be used in the adjustment or operation of internal combustion engines. However, while modern technology has made it possible to do so, there are as yet no such devices in popular use. This is due primarily to the cost involved in implementing the sophisticated electronic means which are necessary.
It is therefore an object of the present invention to provide apparatus for manifesting the torque being developed in an internal combustion engine.
Another object of the invention is to provide an economical apparatus for indicating engine power.
Another object is to provide a method for determining the torque and/or power being developed by an internal combustion engine.